Process for treating tars

ABSTRACT

THE PROCESS FOR TREATING TARS OF THIS INVENTION COMPRISES STEPS OF (1) HEATING A STARTING TAR TO A TEMPERATURE OF 320 TO 470*C. UNDER INCREASED PRESSURE OF 1 TO 20 KG./CM.2 GAUGE TO PRODUCE GAS, OIL AND PITCH, (2) SEPARATING OIL AND PITCH BY DISTILLATION TO PRODUCE PITCH HAVING A SOFTENING POINT OF AT LEAST 60*C. AND CONTAINING 20 TO 45% BY WEIGHT OF BENZENE-INSOLUBLE CONTENT AND 3 TO 20% BY WEIGHT OF QUINOLINE-INSOLUBLE CONTENT, (3) HEATING THE RESULTING OIL UNDER INCREASED PRESSURE OF 3 TO 35 KG./CM.2 GAUGE AT A TEMPERATURE RANING FROM 370 TO 540*C. AND AT LEAST 10*C. HIGHER THAN THE HEATING TEMPERATURE IN THE FIRST STEP TO PRODUCE GAS, OIL AND PITCH, AND (4) SEPARATING OIL AND PITCHED BY DISTILLATION TO PRODUCE PITCH HAVING A SOFTENING POINT OF AT LEAST 60*C. AND CONTAINING 15 TO 40% BY WEIGHT OF BENZENE-INSOLUBLE CONTENT AND NOT MORE THAN 2% BY WEIGHT OF QUINOLINE-INSOLUBLE CONTENT.

United States Patent 015cc 3,692,663 Patented Sept. 19, 1972 3,692,663PROCESS FOR TREATING TARS Koza Ueda, Kyoto, Jitsurni Kimoto, Takarazuka,and Mitsuru Moritake, Suita, Japan, assignors to Osaka Gas Company,Limited, Osaka-shi, Japan No Drawing. Filed Mar. 19, 1971, Ser. No.126,356 Int. Cl. Cc 3/02 US. Cl. 208-44 8 Claims ABSTRACT OF THEDISCLOSURE The process for treating tars of this invention comprisessteps of (l) heating a starting tar to a temperature of 320 to 470 C.under increased pressure of l to 20 kg./cm. gauge to produce gas, oiland pitch, (2) separating oil and pitch by distillation to produce pitchhaving a softening point of at least 60 C. and containing 20 to 45% byweight of benzene-insoluble content and 3 to 20% by weight ofquinoline-insoluble content, (3) heating the resulting oil underincreased pressure of 3 to 35 kg./cm. gauge at a temperature rangingfrom 370 to 540 C. and at least 10 C. higher than the heatingtemperature in the first step to produce gas, oil and pitch, and (4)separating oil and pitch by distillation to produce pitch having asoftening point of at least 60 C. and con taining to 40% by weight ofbenzene-insoluble content and not more than 2% by Weight ofquinoline-insoluble content.

This invention relates to a novel process for treating tars.

In general, tar resulting from dry distillation of coal or cracking ofpetroleum is treated principally for the purpose of recovering oils, andpitch is obtained as a resulting byproduct. In most tar industries, taris subjected to distillation under atmospheric or reduced pressure toobtain light, middle and heavy fractions for use as industrial materialsand a residue is recovered as pitch. The resulting pitch is utilized asa binder for producing electrodes, as an impregnating agent for bakedelectrodes to improve mechanical and electric properties of theelectrodes and as an additive to be added to coking coal charge inproducing coke to improve the qualities of the coke. However, the pitchproduced by such method has limited properties with the result that thepitch can be used only for the restricted applications and purposes.

The properties of pitch are generally represented by solubility insolvents: pitch is divided into benzene-soluble content andbenzene-insoluble content, the benzene-insoluble content further beingdivided into quinoline-soluble and quinoline-insoluble contents. Pitchobtained by conventional methods generally has a softening point in excess of 60 C. and contains to 40% by Weight of benzene-insoluble contentand 5 to 20% by Weight of quinoline-insoluble content. With respect tosuch properties, increase in benzene-insoluble content inevitablyresults in greater quinoline-insoluble content. On the contrary, if itis attempted to lower the quinoline-insoluble content, thebenzene-insoluble content will also be lowered with increasedbenzene-soluble content. In many cases, however, the amount of bothbenzene-insoluble content and quinoline-insoluble content, and thedifference between these two amounts are critical factors to determinethe properties of pitch. For instance, if it is desired to obtain anelectrode having improved properties in strength, density and specificelectric resistance by using pitch as a binding agent, it is requiredthat the pitch have at least by weight of benzene-insoluble content andlow quinolineinsoluble content and that the component (so-called 8-resin) accounting for the dilference between the benzeneinsolublecontent and the quinoline-insoluble content be at least 20% by weight.Notwithstanding this, it has been difiicult to obtain pitch satisfyingsuch requirements, since an attempt to increase benzene-insolublecontent to more than 30% by weight is accompanied by a correspondingincrease in quinoline-insoluble content. Further it is desired thatpitch to be used as an impregnating agent for baked electrodes have thelowest possible quinoline-insoluble content. More specifically, it isrequired for the pitch to contain not more than 3 by weight ofquinolineinsoluble content and at least 20% by weight ofbenzeneinsoluble content. With a conventional method, however,preparation of pitch having not more than 3% by weight ofquinoline-insoluble content encounters a consequent difliculty that thebenzene-insoluble content lowers to about 15% by weight or less with apredominant amount being benzene-soluble content, this making itimpossible to obtain pitch for use as an impregnating agent which hasdesired properties. Thus, with conventional method, pitch obtained hadrestricted properties and it Was impossible to control properties ofpitch as desired in conformity with various uses and purposes.

An object of this invention is to provide a process by which pitchuseful for a wide variety of applications can be recovered in high yieldby treating tars under increased pressure unlike conventionaldistillation treatment and by which thermally stable oils havingexcellent qualities and gases employable as a fuel source can also berecovered.

Another object of this invention is to provide a process for treatingtars by which amounts of benzene-insoluble content andquinoline-insoluble content can be controlled individually and which istherefore capable of providing pitch satisfying every requirementinvolved in various uses and purposes.

Another object of this invention is to provide a process for treatingtars whereby useful pitch having peculiar characteristics can beprepared by each step of multi-step heat treatment and by mixingrespective pitches obtained by respective steps.

Another object of this invention is to provide a process for treatingtars whereby pitch can be obtained in high yield of at least by weightbased on tars without coking diificulties.

Still another object of this invention is to provide a process fortreating tars which is capable of producing oil of high quality almostfree of unstable components as byproduct.

The above and other objects of this invention will become more apparentfrom the following description.

The process for treating tars of this invention comprises steps of (l)heating a starting tar to a temperature of 320 to 470 C. under increasedpressure of 1 to 20 kg./cm. gauge to produce gas, oil and pitch, (2)separating oil and pitch by distillation to produce pitch having asoftening point of at least 60 C. and containing 20 to 45% by weight ofbenzene-insoluble content and 3 to 20% by weight of quinoline-insolublecontent, (3) heating the resulting oil under increased pressure of 3 to35 kg./cm. gauge at a temperature ranging from 370 to 540 C. and atleast 10 C. higher than the heating temperature in the first step toproduce gas, oil and pitch, and (4) separating oil and pitch bydistillation to produce pitch having a softening point of at least 60 C.and containing 15 to 40% by weight of a benzene-insoluble content andnot more than 2% by weight of quinolineinsoluble content.

The softening point as used in this specification and claims is a valuedetermined in accordance with mercury method set forth in 118 (JapaneseIndustrial Standards) K 2421-66.

In accordance with this invention, tar is heated under increasedpressure during two steps of heat treatment, whereby pitch havingparticular characteristics can be obtained by each step of heattreatment operation. More specifically, when tar is heated to 320 to 470C. directly under increased pressure of 1 to 20 kg./cm. gauge, pitchcontaining 20 to 45 by weight of benzene-insoluble content and 3 to 20%by weight of quinoline-insoluble content can be obtained in high yieldtogether with gas and oil. Pitch having such properties fully meets therequirements of various uses and can be used as a binder for electrodes,an impregnating agent for baked electrodes and an additive for coal.Although increase of the benzene-insoluble content may result inincrease of quinolineinsoluble content, the increase is much smallerthan is the case with the conventional method. Even where thebenzene-insoluble content exceeds 30% by weight, at least 23% by weightof the fl-resin component can be retained, this showing a particularadvantage that the pitch can be used as a binder in producing electrodeshaving more excellent properties than conventionally possible. In fact,in the case where pitch prepared in accordance with this invention andcontaining fi-resin content exceeding 23% by weight is used as a binder,electrodes produced have improved bending strength, compression strengthand specific electric resistance. The fact that pitch with suchproperties can be obtained is attributable solely to the foregoing heattreatment which is carried out under increased pressure so as topositively convert effective components in tar to pitch. Such result cannot be obtained by conventional methods of distillation whereintreatment is conducted under atmospheric or reduced pressure.

In accordance with the present invention, oil resulting from the firststep of heat treatment is then treated under severer conditions than inthe first step, whereby pitch containing a very low quinoline-insolublecontent is prepared. Despite the fact that pitch obtained by the secondstep of heat treatment contains 15 to 40% by weight of benzene-insolublecontent, the amount of quinoline-insoluble content is even lower than 2%by weight. Such pitch is very suitable for uses wherein a suflicientlygreat amount of benzene-insoluble content and a relatively small amountof quinoline-insoluble content are essential as in the case ofimpregnating agent for baked electrodes. A baked electrode impregnatedwith pitch of this invention having a low quinoline-insoluble contenthas exceedingly improved bending strength, compression strength andspecific electric resistance. Moreover, since the pitch resulting fromthe first step of heat treatment is distinct from the pitch obtainedfrom the second step of heat treatment in properties, especially inquinolineinsoluble content, both pitches, when mixed together, can beformed into pitch of desired properties. Thus, the pitch of thisinvention can be applied to wider uses and purposes because of excellentproperties. In additoin, since the oil from the first step of heattreatment is converted into pitch in the second step of heat treatment,the total yield of pitch can be substantially increased and the oilproduct obtained only from the second step of heat treatment is almostfree of unstable components. A high quality oil very useful as anabsorbent will be thus produced. In accordance with this inventionwherein tar is converted to pitch by a two-step heat treatment, it ispossible to convert unstable components to pitch through the first stepof heat treatment so that coking will not be likely to take place nor'will troubles arise in operation or in apparatus even when the productsare treated under severer conditions during the second step of heattreatment.

The softening point of pitch obtained from each step of heat treatmentcan be adjusted over a wide range as desired by varying heat treatmentconditions as well as conditions of distillation conducted after theheat treatment, namely by varying the amount of low-boiling frac- 4tion. Generally, the softening point of pitch is in the range of about60 to C., though it is possible to obtain pitch having higher softeningpoint of 150 to 300 C.

The tars to be used as starting material of this invention includecoal-tar and oil gas tar produced by thermal or catalytic cracking ofpetroleum, the tars being such that they have an absolute viscosity of20 to 1000 centipoises at 50 C. and containing 5 to 30% by weight of0270 C. fraction and 25 to 45% by weight of 0-360 C. fraction.Particularly preferable are tars having an absolute viscosity of 50 to200 centipoises at 50 C. and containing 15 to 25% by weight of 0-270 C.fraction and 30 to 40% by weight of 0 to 360 C. fraction.

In accordance with the method of the present invention the starting taris heated to 320 to 470 C. under increased pressure of 1 to 20 kg./cm.gauge, whereby effective components in the starting tar are positivelyconverted to pitch. More specifically, heavy fraction and relativelylowboiling, unstable condensed ring substances undergo condensationpolymerization to be converted to pitch, while unreacted components areobtained as an oil fraction together with a gaseous reaction product.During this step, the reaction temperature of 320 to 470 C. is ofimportant significance: a temperature lower than 320 C. fails to effectthe reaction satisfactorily, whereas a temperature in excess of 470 C.gives rise to coking in the reactor. The reaction may preferably becarried out at a temperature of 380 to 430 C. It is required to effectthe reaction in this step under increased pressure of l to 20 kg./cm.gauge, whereby the substances to be reacted in the tar can be retainedin a liquid phase to insure positive conversion to pitch. There is aneed to avoid treatment under an atmospheric or reduced pressure,because such treatment would allow relatively low-boiling, unstablecondensed ring substances to be left unreacted without subjecting thesubstances to condensation polymerization for conversion to pitch, thisnot only preventing formation of pitch with good quality but causingcoking within the reactor during the second step of heat treatmentconducted under severe reaction conditions. On the contrary, when thepressure exceeds 20 kg./cm. gauge, better results will not be achievedand troubles will be encountered with apparatus and operation. Suitablepressure for the reaction at this stage is therefore in the range of 5to 15 kg./cm. gauge. The reaction time may vary over a wide rangedepending upon the reaction conditions and properties of pitch to beobtained, but usually the reaction is completed in about 1 to 20 hours.

The first step of heat treatment results in the production of gas, oiland pitch. The gas is taken out from the system for the use in fuelsource and the resulting mixture of oil and pitch is subjected todistillation for separation. The pitch thus obtained has a softeningpoint of at least 60 C. and containing 20 to 45% by weight ofbenzene-insoluble content and 3 to 20% by weight of quinoline-insolublecontent.

Oil obtained in the first step of heat treatment is further heated inthe subsequent second step of heat treatment, wherein reaction iseffected at a temperature at least 10 C. higher than that applied in thefirst step of heat treatment. During this step, components leftunreacted in the preceding heat treatment step are positively convertedto pitch. The reaction temperature is in the range of 370 to 540 C.,while the reaction pressure is 3 to 35 kg./cm. gauge. Reactiontemperature lower than that in the first step of heat treatment or below370 C. retards reaction for conversion to pitch, making it difiicult toobtain desired pitch, whereas a temperature exceeding 540 C. gives riseto coking. The reaction temperature may preferably be in the range of420 to 460 C., which is 30 to 60 C. higher than that applied in thefirst heat treatment step. Further reaction pressure lower than 3kg./cm. gauge will cause low-boiling components to evaporate off anddeteriorate pitch yield, producing adverse effects on properties. On theother hand, a pressure exceeding 35 kg./cm.'- gauge will merely causetroubles to apparatus or result in ditficulties in operation withoutproducing any improvement in efiiciency. The pressure may preferably be7 to 20 kg./cm. gauge. The reaction for the second heat treatment stepis generally completed in 1 to 40 hours although the reaction timevaries over a wide range depending upon the reaction conditions and theproperties of pitch to be produced.

In the second heat treatment step gas, oil and pitch are obtained, andduring the operation gas is taken out from the system for the use infuel source. The resulting mixture of oil and pitch is subjected todistillation for separation. The pitch obtained from this step has asoftening point of at least 60 C. and peculiar properties in that itcontains 15 to 40% by weight of benzene-insoluble content and anexceedingly small amount of, i.e. not more than 2% by weight of,quinoline-insoluble content. It has been impossible for a conventionalmethod to produce such pitch that contains very small amount ofquinoline-insoluble content in spite of high-benzene-insoluble contentwhich amounts to 15 to 40% by weight. Indeed, the pitch thus preparedfinds versatile aplications, for instance, as an impregnating agent forbaked electrodes. This invention further has a particular advantage thatthe pitch obtained by the second heat treatment step can be mixed withthe pitch prepared by the first heat treatment step to readily preparepitch of desired properties. The oil obtained by the present process hasexcellent thermal stability and is used as good absorbent since unstablecomponents have been converted to pitch by the two steps of heattreatment.

The present invention has been described with respect to a case whereintar is treated by two steps of heat treatment operation. However, inaccordance with this invention tar can further be treated by amulti-step heat treatment. That is, the oil produced by the second heattreatment step will then be treated thermally under severer conditions,for instance, at a temperature ranging from 380 to 560 C. and at least10 C. higher than that in the second step under a pressure of 3 to 35kg./cm. gauge. Pitch produced by such multi-step heat treatment haspeculiar properties and contains much lower quinolineinsoluble content.It is desired to employ such multi-step heat treatment depending uponrequirements in uses of pitch.

The method of the invention can be conducted by batch method as well asin continuous manner.

For a better understanding of the invention examples are given below, inwhich percentages are by weight.

EXAMPLE 1 Crude coal tar was passed through a wetted-wall tower at 84 C.to remove water contained therein. The dried tar had an absoluteviscosity at 50 C. of 102.4 cps. and contained 17.1% of a fractionboiling at to 270 C. and 36.8% of a. fraction boiling at 0 to 360 C. Thetar was placed in an autoclave equipped with a partial condenser andpressure regulator and heated at 400 C. under 9 kg./ cm. gauge forhours. The vapor produced was condensed in the partail condenser forrefluxing and noncondensed gas was taken out from the system. The tarthus treated was subjected to isothermal flash distillation to separatepitch and oil.

The yields of the pitch, oil and gas thus obtained and the properties ofthe pitch are shown in Table 1.

The oil obtained in the first heat treatment step was then placed in anautoclave with a partial condenser and pressure regulator. The oil inthe autoclave was heated at 450 C. under 12 kg./cm. gauge for hours. Thevapor produced was condensed in the partial condenser for refluxing andnon-condensed gas was taken out of the system. Oil thus treated wassubjected to isothermal flash distillation to separate pitch and oil.

6 The yields of the pitch, oil and gas thus obtained and the propertiesof the pitch and oil are shown in Table 1 below.

TABLE 1 First Second heat heat treattreatment ment step step Gas 0. 9 2.1

Properties: pitch:

Soitening point C.) 80. 5 81. 0 Volatile substance (percent) 45. 8 46. 9Quinoline-insoluble content (percent) 7. 2 0.7 Benzene-insoluble content(percent) 32. 0 28. 7 Properties; oil:

Specific gravity 1. 06 Temperature for 20%-distlllation C.) 221Temperature for 50%distillation C.) 252 Temperature for distillation C.)336 Acenaphthene content (percent) Trace EXAMPLE 2 Dried coal tar thesame as in Example 1 was heattreated under the same conditions as inExample 1, and the oil obtained in the second heat treatment step wasthen placed in an autoclave equipped with a partial condenser andpressure regulator and heated at 460 C. under a pressure of 20 l g./crn.gauge for 2 0 hours. The product thus treated was subjected to flashdistillation to separate pitch and oil. The yield of the pitch based onthe weight of the oil from the second step was 36.5%, and the propertiesthereof are shown in Table 2 below.

TABLE 2 Softening point C.) 82 Quinoline-insolubie content (percent) 0.2Benzene-insoluble content (percent) 15.2

EXAMPLE 3 Dried coal tar the same as in Example 1 was heattreated in thesame manner as in Example 1, except that the conditions applied in thefirst and second heat treatment steps were changed as shown in Table 3below, in which are also disclosed the properties of the pitch and oilobtained in respective steps.

TABLE 3 First Second heat heat treattreatment ment step step Conditions:

Temperature C.) 360 430 Pressure (kg/cm. G)- 5 8 Time (hours) 18 20Yield, percent:

Pi 55.1 61. 1 Oil 44. 6 37. 2 POrG as 0. 3 l. 7

perties; pitch: Softening point C.) 76.0 70. 5 Volatile substance(percent) 48. 2 47. 3 Quinoline-insoluble content (percent) 8. 4 1. 6ProBenzeneinsoluble content (percent) 35. 2 28.1

perties; oil: Specific gravity 1. 04 Temperature ior 20%-distillationC.). 217 Temperature for 50%-distillation C.) 248 Temperature tor80%-distiilation C.) 330 Acenaphthene content (percent) Trace EXAMPLE 4Dried coal tar the same as in Example 1 was heattreated in the samemanner as in Example 1, except that the conditions applied in the firstand second treatment steps were changed as shown in Table 4 below, inwhich are also disclosed the properties of the pitch and oil obtained inrespective steps.

TABLE 4 First Second heat heat treattreatment ment step step Conditions:

Temperature C.) 460 490 Pressure (kg/cm. G) 20 20 Time (hours). 2 2Yield:

Pitch 71. 2 40. 6 Oi1--- 26.0 57.0 Gas 2. 8 2. 4 Properties; pitch:

Softening point C.) 85. 3 84. 5 Volatile substance (percent) 44.3 49.Quinoline-insoluble content (percent). 10. 0. l Benzene-insolublecontent (percent) 36. 1 20. 3 Properties; oil:

Specific gravity 1.08 Temperature for 20%-distillation C 231 Temperaturefor 50%-distillation 0.). 250 Temperature for 80%-distillation C.) 334Acenaphthcne content (percent) Trace EXAMPLE 5 Crude oil gas tar wasdried in the same manner as in Example 1 to obtain dried tar having anabsolute viscosity at 50 C. of 28.7 cps. and containing 20.3% of afraction boiling at 0 to 270 C. and 35.0% of a fraction boiling at 0 to360 C. The dried tar was then subjected to the heat treatment in thesame manner as in Example 1, except that the conditions applied in thefirst and second heat treatment steps were changed as shown in Table 5below, in which are also shown the properties of the pitch and oilobtained in each step.

TABLE 6 First Second heat heat treattreatment ment step step Conditions:

Temperature C.) 385 450 Pressure (kg/cm. G) 9 9 Time (hours) 5 Yield;(percent):

Pitch 59. 3 48. 6 39.6 48.0 Gas 0. 7 3. 4 Properties; pitch:

Softening point C C.) 79. 8 76. 0 Volatile substance (percent) 47. 2 48.0 Quinoline-insoluble content (percen 8. 4 2.0 Benzene-insoluble content(percent)- 34. 2 31. 3 Properties; oil:

Specific gravity 1 04 Temperature [or 20%-distillation C.) 216Temperature for 50%-dlstillation C.) 247 Temperature for80%-distillation C.) 340 Acenaphthene content (percent) Trace Forcomparison tar was treated in the following manners:

Comparison I Coal tar the same as in Example 1 was distilled at 310 C.under atmospheric pressure and the residue was further distilled at 345C. under reduced pressure of --0.85 kg./cm. gauge. Thus pitch and oilwere obtained in yields of 54.9% and 45.1% respectively, based on theweight of the starting coal tar used. The properties thereof are shownin Table 6 below.

Comparison 11 The pitch obtained in Comparison I was further heated at400 C. under atmospheric pressure for 5 hours. The properties of thepitch thus obtained are shown in Table 7 below.

Table 7 Softening point 0.) 82 Quinoline-insoluble content percent 17.1Benzene-insoluble content percent 37.0

Comparison III The oil obtained from distillation under reduced pressurein Comparison I and having the following properties was subjected toheat treatment under the same conditions as applied in the second stepof heat treatment in Example 1. During the treatment coking occurred toproduce rigid solid containing 82.0% of quinoline-insoluble content in ayield of 13% based on the weight of the oil used.

The properties of the oil used were as follows:

Absolute viscosity cps. at C... 5.8 Content of 0 to 270 C. fraction"percent" 0 Content of 0 to 360 C. fraction percent 50 What we claim is:

1. A process for treating tar which comprises steps of:

(l) heating starting tar to a temperature of 320 to 470 C. underincreased pressure of l to 20 kg./cm. gauge to produce gas, oil andpitch,

(2) separating oil and pitch by distillation to obtain pitch having asoftening point of at least 60 C. and containing 20 to 45% by weight ofbenzene-insoluble content and 3 to 20% by weight of quinoline-insolublecontent,

(3) heating the resulting oil under increased pressure of 3 to 35kg./cm. gauge at a temperature ranging from 370 to 540 C. and at least10 C. higher than the heating temperature in the first step to producegas, oil and pitch, and

(4) separating oil and pitch by distillation to obtain pitch having asoftening point of at least 60 C. and containing 15 to 40% by weight ofbenzene-insoluble content and not more than 2% by Weight ofquinolineinsoluble content.

2. The process according to claim 1, in which said tar has an absoluteviscosity at 50 C. of 20 to 1000 cps. and contains 5 to 30% by weight of0 to 270 C. fraction and 25 to 45 by weight of 0 to 360 C. fraction.

3. The process according to claim 2, in which said tar has an absoluteviscosity at 50 C. of 50 to 200 cps. and contains 15 to 25% by weight of0 to 270 C. fraction and 30 to 40% by weight of 0 to 360 C. fraction.

4. The process according to claim 1, in which said first heat treatmentstep for the starting tar is conducted at a temperature of 380 to 430 C.under increased pressure of 5 to 15 l g./cm. gauge.

5. The process according to claim 1, in which said second heat treatmentstep for the oil resulting from said first heat treatment step isconducted at a temperature of 420 to 460 C. under increased pressure of7 to 20 kg./cm. gauge.

6. The process according to claim 5, in which said temperature in thesecond heat treatment step is a temperature of 30 to 60 C. higher thanthat applied in the first heat treatment step.

7. The process according to claim 1, in which said pitch obtained in thefirst heat treatment step is mixed with the pitch obtained in the secondheat treatment step to adjust the properties of the pitch.

8. The process according to claim 1, in which said oil obtained from thesecond heat treatment step is further heat-treated under increasedpressure of 3 to 35 kg/cm. gauge at a temperature ranging from 380 to560 C. and

References Cited UNITED STATES PATENTS 2,985,577 5/1961 Geller et a1.20844 X 2,992,181 7/1961 Renner 20844 X 3,190,812 6/1965 Puls 20844 X 10FOREIGN PATENTS 628,474 10/1961 Canada 20844 5 DELBERT E. GANTZ, PrimaryExaminer US. Cl. X.R. 20822 Patent No.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIUN l 3,692,663 Dated.September 19, 1 972 Inventor(s) Kozo' Ueda Jitsumi Kimoto and MitsuruMoritake It is certified that error appears in the above-identifiedpatentand that said' Letters Patent are hereby corrected as shown below:

In the heading insert Claims priority of Japahese Application .Serial'No. 37646/70, filedMay 1, 1970 Signed and sealed this 'Sth day of May1973-.

11013331 GOTTSCHALK K 11 '..Z-l'..-LJT 3I-iiikjl,J'H. .6

Commissioner of Patents usco'MlwDc G0376-F'69 U.5. GOVERNHENY PRINTINGOFFICE: I969 0-366334

